A second U.S. Embassy staffer in Kyiv overheard a cellphone call between President Donald Trump and his ambassador to the European Union discussing a need for Ukrainian officials to pursue “investigations,” The Associated Press has learned.

The July 26 call between Trump and Gordon Sondland was first described during testimony Wednesday by William Taylor, the acting U.S. ambassador to Ukraine. Taylor said one of his staffers overhead the call while Sondland was in a Kyiv restaurant the day after Trump’s July 25 phone call with Ukrainian President Volodymyr Zelenskiy that triggered the House impeachment inquiry.

The second diplomatic staffer also at the table was Suriya Jayanti, a foreign service officer based in Kyiv. A person briefed on what Jayanti overheard spoke to AP on condition of anonymity to discuss a sensitive matter currently under investigation.

The accounts of the two embassy staffers could tie Trump closer to alleged efforts to hold up military aid to Ukraine in exchange for investigations into political rival Joe Biden and his son Hunter’s business dealings. In defending Trump on Wednesday, Republicans repeatedly highlighted that Taylor never directly heard the president direct anyone to demand that the Ukrainians open the probe.

Trump on Wednesday said he did not recall the July 26 call with Sondland.

“No, not at all, not even a little bit,” Trump said.

The White House did not respond to questions Thursday about the second witness to the call with Sondland.

The staffer Taylor testified about is David Holmes, the political counselor at the embassy in Kyiv, according to an official familiar with the matter who spoke on condition of anonymity.

Holmes is scheduled to testify Friday before House investigators in a closed session.

Taylor was one of the first witnesses called Wednesday during the impeachment inquiry’s initial open hearing. He testified that his staffer could hear Trump on the phone asking Sondland about “the investigations.”

Later that day, a Twitter account that appears to belong to Ukraine’s then-Defense Minister Oleksandr Danylyuk posted a photo of himself at dinner with Sondland, Taylor and Ambassador Kurt Volker, who was then Trump’s special envoy to Ukraine for peace negotiations.

Since 2014, the Ukrainian government has been battling Russian-backed separatists in the country’s eastern region, and the continuation of U.S. military aid is crucial to its defense. Whether Trump directed nearly $400 million in aid to be withheld to force the Ukrainians to open investigations into Democrats is a key question of the impeachment inquiry.

Current and former U.S. officials say Sondland’s use of a cellphone in a public place in Ukraine to speak with anyone in the U.S. government back home about sensitive matters, let alone the president, would be a significant breach of communications security.

Jayanti is an attorney who joined the State Department in 2012 and was previously posted at the U.S. Embassy in Iraq. She has been stationed since September 2018 at the embassy in Kyiv where she helps coordinate U.S. business interests with the former Soviet republic’s energy industry.

Jayanti was in Washington last month and scheduled for a closed-door interview with impeachment investigators. But the deposition was canceled because of the funeral for former House Oversight Chair Elijah Cummings and has not yet been rescheduled.

Holmes, a career diplomat, joined the Foreign Service in 2002 and has served in Afghanistan, Colombia, India, Kosovo and Russia as well as on the White House National Security Council staff. He won an award for constructive dissent from the American Foreign Service Association in 2014 for complaining about problems that an alternate diplomatic channel had caused in South Asia and recommending organizational changes to the State Department’s bureaucratic structure for the region.

U.S. diplomats and other government employees are instructed not to use cellphones for sensitive official matters while traveling anywhere abroad and notably in countries known to be targeted for surveillance by intelligence agencies such as Russia, China and Israel.

Ukraine has long been among the countries of concern, particularly since a 2014 incident in which the U.S. accused Russian intelligence of eavesdropping on and then leaking a recording of a conversation between two senior U.S. officials in Kyiv that led to great embarrassment and strains between the U.S. and its European allies.

In that recording, then-Assistant Secretary of State for European Affairs Victoria Nuland is heard telling former U.S. Ambassador to Ukraine Geoff Pyatt “F-ck the EU,” because of the European Union’s slowness to respond to the political crisis in the country.

“That phone call was also a mistake the way it was conducted and it had huge implications for our foreign policy,” said Michael McFaul, a former U.S. ambassador to Russia who is now at Stanford University. “Particularly after that, anybody should understand how dangerous it is to make an unsecured call in Kyiv, or anywhere else for that matter.”

“Obviously, making a phone call from Kyiv to the president of the United States means that not just the Russian intelligence services will be on the call, but a whole lot of other people, too,” McFaul said. “If it was that important, he (Sondland) could have easily gotten up from the restaurant, gone to the embassy and made a secure call through the White House operations center.”

Steven Pifer, who served as U.S. ambassador to Ukraine from 1998 to 2000, said he always assumed his cellphone calls were being monitored and would not discuss anything sensitive unless he was on a secure phone at the embassy or his residence.

“Any unsecure call is vulnerable, but there’s a special risk if it’s the president’s number on your phone,” Pifer said. “You have to know everyone is going to be interested in it and not just the Russians.”

In a closed-door hearing last month, former White House Russia adviser Fiona Hill said she was concerned that Sondland posed a counterintelligence risk, according to a transcript released by the House. Hill cited a Sondland habit of giving out personal cellphone numbers — hers and national security adviser John Bolton’s as well as his own — and his failure to get appropriately briefed ahead of meetings.

“So he was often meeting with people he had no information about,” said Hill, who served as the senior director for Russia at the National Security Council. “It’s like basically driving along with no guardrails and no GPS on an unfamiliar territory.”

She said Sondland was meeting with foreign officials “that we had derogatory information on that he shouldn’t have been meeting with” or he was giving out his phone number or texting foreign officials. “All of those communications could have been exfiltrated by the Russians very easily,” she said.

Hill said officials from Europe would literally appear at the gates of the White House and call her personal phone, which was kept in a lockbox. She said she’d later find messages from irate officials who’d been told by Sondland that they were supposed to meet with her.

She said she found it deeply concerning and asked for someone from the Intelligence Bureau to “sit down with him and explain that this was a counterintelligence risk.”