A dump truck hauling dirt at a construction site near West Grant and North Oracle roads knocked down two power poles Thursday morning, authorities said.

Tucson Electric Power Co. crews were working to replace the power poles, and are expected to work through the night, said Michael Graham, a city spokesman.

Oracle Road south of Grant Road is expected to be closed until 6 a.m. Friday, Graham said.

Southbound travel on Oracle is being detoured to either eastbound or westbound Grant Road, Graham said.

Motorists traveling north on Oracle are being diverted to either Speedway or Drachman Street, said Graham.

The incident occurred shortly after 8 a.m. when the truck driver left the bed of the dump truck up after unloading dirt, said Sgt. Chris Widmer, a Tucson Police Department spokesman.

The bed brought down the powerlines, and poles, Widmer said.

Some 3,600 TEP customers lost power, said Joseph Barrios, a spokesman for the electric company. Power was restored to all the customers, except one commercial customer who remained without power Thursday evening, Barrios said.