More than 20 people treated for heat-related injuries at Union Pacific Big Boy event in Berks County, Pennsylvania

More than 20 people were treated for heat-related injuries Thursday at a Union Pacific Big Boy whistle stop event in Berks County, Pennsylvania, police said.

Muhlenberg Township Police Department Chief Randall Hoover told CBS News Philadelphia that several of the people were taken to hospitals for treatment. At least one person suffered cardiac arrest, but one person is believed to be OK, Hoover said. 

Chopper 3 was over the scene at Muhlenberg Park in Berks County, showing a large EMS presence and a crowd of people.

Medics were seen caring for people who may have been impacted by the heat. At least one person was taken out on a stretcher. Several ambulances were on scene and tents and cooling buses were seen in the area.

Hoover said they ran out of emergency medical service personnel at the event and had to call in help from neighboring Chester and Montgomery counties. 

A large group of people had gathered at the train station to watch the Big Boy historic train roll through the area. The train rolled through and is on its way to its next stop, scheduled in Pottstown. The borough of Pottstown told CBS News Philadelphia there are currently no changes to its watch party for the Big Boy.

Union Pacific said Big Boy will be slowing down because of the heat, but plans on being in Pottstown by 5:45 p.m.

The Big Boy is scheduled to roll through Philadelphia on the Fourth of July.

Parts of Berks County are seeing 103-degree temperatures and feel-like temps worse than that as the region is in the middle of a dangerous heat wave.

This is a developing story and will be updated.