Five people, including a pregnant woman, a mother and her two daughters, were injured in a three-vehicle crash near Acton Tuesday morning that left a propane truck overturned and leaking propane and prompted the evacuation of nearby businesses.

The crash happened shortly before 9:15 a.m. on the southbound lanes of Highway 14, just south of Crown Valley Road, involving an RV, a propane truck and a Toyota Yaris.

Critically hurt in the crash were three adult women and a 12-year-old girl.

The mother and a 19-year-old female passenger, described as pregnant, were traveling southbound in a Yaris on Highway 14 behind the RV driven by the 21-year-old.

The driver of the propane truck rear-ended the Yaris, sending it into the back of the RV, Officer Gil Hernandez of the California Highway Patrol said.

The impact left the 21-year-old and her sister, trapped inside the disabled RV as the propane truck – overturned on its side on the shoulder – began leaking, emergency response officials said.

Firefighters worked to free the RV occupants from the vehicle as hazardous material crews were dispatched to the overturned propane truck.

Also dispatched to land on Highway 14, once traffic was stopped, was the Air Rescue 5 helicopter.

Once the two younger patients were freed from the RV, the 12-year-old and her mother were airlifted Northridge Hospital Medical Center, both critical.

The other two women, the 19-year-old and the 21-year-old, were taken by ambulance to Antelope Valley Hospital.

Treated for moderate injuries and taken by ambulance to a hospital in the Antelope Valley was the driver of the propane truck.

“When firefighters arrived they found people in the RV needed extrication,” Brian Stevens, spokesman for the Los Angeles County Fire Department said, noting firefighters arrived at the crash at 9:24.

Hernandez said the Yaris was traveling at a slow speed in the number three lane when “it was impacted by the propane truck.”

“The Yaris hit the RV, leaving it partially overturned,” Hernandez said.

Once all five patients were taken to the hospital, attention shifted to the overturned propane truck.

“Right now, we’re releasing the gas, venting the propane, and allowing some of the gas to escape,” Hernandez said at 11:45 a.m.

“Once it (truck) is deemed safe they’re going to right it,” he said.

All southbound lanes of Highway 14 were shut down with southbound motorists being allowed to travel down the center median.

The CHP expects the lanes to remain closed for about three hours.

“We set up a 500-foot perimeter around the propane truck,” Stevens said, describing the truck as hauling 2600 gallons of propane.

“We also evacuated nearby businesses,” he said.

Health HazMat crews were also dispatched to the site.