Two dead human bodies were recovered on Thursday morning inside a vehicle submerged in a flooded Millbrae underpass, authorities confirmed, KPIX 5 reported.

According to the San Mateo County Sheriff’s Office spokesperson, reports of flooding reached the firefighters who responded at the location at Hemlock Ave. and E. Hillcrest Blvd. in Millbrae, at about 5:45 in the morning.

“Upon arrival, they noticed a person standing on the roof of a vehicle. The fire department entered the water to rescue the person in the vehicle. While doing that they realized that there was a second vehicle in the water,” Sheriff’s Detective Javier Acosta said. “So after they rescued the first person, they tried to gain access to the vehicle in the water. However, the conditions changed rapidly and it became too dangerous for the responders. The water was rising very rapidly and they had to retreat.”

Crews allotted many hours draining water in the location, Acosta said.

The firefighters then saw two dead people inside a second vehicle they were able to access.

“At this time we don’t know exactly what happened,” said Acosta. “However, there was heavy rain this morning.”

The area was included in many low-lying places in the county that experience flooding after an overnight rainstorm. A flood advisory was released by the National Weather Service for the area and cautioned that flooded crossings may be obstructed.

“We are responding to multiple flooding calls across the coastal area in San Mateo County,” according to officials of Cal Fire on Thursday morning.

The investigation was conducted on the area of the incident, which temporarily closed the E. Hillcrest Blvd. between Hemlock and Aviador avenues. Hillcrest was opened for traffic in both directions just after 2 p.m., the sheriff’s office said.