The rail car in question is parked along Parkside Drive, not far from homes.

Union Pacific workers were doing a routine inspection when they noticed something was amiss on one car and thought there was a leak.

Since each tanker car carries about 30,000 gallons of highly flammable butane, the workers called Contra Costa County Fire Department for help.

“Absolutely it’s a scare. We want to make sure everybody was as safe as possible,” said Fire Marshall Robert Marshall.

Fire crews evacuated half a dozen nearby homes.

“I just heard the helicopters and stepped outside to see what was going on,” said Brian Gillespie, a neighbor. People in the area were alerted by the commotion of the fire crews and police descending on their neighborhood.

“My concern was just the safety of the people in the area,” said Gillespie.

Firefighters called in Contra Costa County’s Hazardous Materials team.

First, they took an air sample from 50 feet away. That test came back negative.

Later, a second team climbed onto the rail car and took a sample of an oily substance that is not usually found on these tankers.

“They ran a test and it came back to be lubricating oil which is not hazardous in this kind of quantity,” said Marshall.

Fire officials lifted the evacuation order at 8:10 p.m.