DALLAS—A crane lowering a heavy length of pipe toppled Thursday morning at a city water pumping station on the Trinity River in Dallas, injuring two city workers.

A contract crew was trying to lower the more than 9-ton pipe through an opening on the pump station roof when it pulled the crane cab off the ground, said Dallas Fire Rescue spokeswoman Sherrie Lopez.

“I think the weight was not distributed properly,” Lopez said.

The boom of the crane fell onto the roof and the pipe landed on two city vehicles, crushing their roofs. The crane’s cab tilted at a 45-degree angle.

A worker in a truck struck by the pipe had a head laceration, Lopez said. A 56-year-old worker on the roof was initially thought to have suffered two broken legs, but Lopez later said it was an ankle injury.

Both workers were taken to Parkland Memorial Hospital and are in good condition, Lopez said.

“We’re very fortunate,” she said. “When you look at the scene, things could have been much worse.”

When the accident happened, three city employees were on the ground, three were in the building and one was on the roof, she said.

She said that the crane company, Louisiana Crane Company, will bring in two more cranes to remove the fallen boom and pipe.

The work was part of routine maintenance on one of the four pumps at the Old Hampton Pumping Station, which takes runoff rain water from city streets and pumps it into the Trinity River, said Kelly High, interim director of street services for the city.

He said the accident’s cause is under investigation.

Patrick Kelley, corporate safety director for Louisiana Crane Company, said Thursday that he was on his way to the scene.