An explosion at a condominium complex injured five people, one critically, on Wednesday in the California mountain community of Mammoth Lakes, authorities said.

The blast occurred shortly before 9:30 a.m. at Val d’Isere Condominiums in the Sierra Nevada. Authorities who arrived on the scene found a building collapsed next to the pool area, the Mammoth Lakes Police Department reported.

They found two men who worked at the complex, including one who had to be freed from snow and debris, police said.

A man then approached and said his wife and son were trapped in their home. The son was located in the bedroom of the collapsed building and the wife was found in the kitchen, police said.

The woman was flown to a hospital in critical condition. The others were taken to a local hospital. Two had moderate injuries and two had minor injuries, police said.

Authorities using dogs searched the area but didn’t find any other victims.

The cause of the explosion was under investigation.

A series of blizzards that began last month have loaded mountains with so much snow that roofs have been crushed and crews have struggled to keep highways clear of avalanches.

However, it wasn’t immediately clear whether the building may have collapsed from snow or the explosion.