Police closed off a north Provo street for more than four hours Thursday afternoon and six people were taken to the hospital in what turned out to be a false alarm for a hazardous-material spill.

Shortly after 1 p.m., members of the Provo Fire Department's hazardous-materials team responded to Smith Megadiamond Inc., 275 W. 2230 North, on a hazardous-spill call. According to firefighter Glen Hart, a truck driver delivering material to the company began complaining of dizziness and a severe headache. The driver was taken to Utah Valley Regional Medical Center for tests.Firefighters suspected the driver's symptoms were the result of a leaking tank of nitric oxide in the back of the truck. Dressed in hazardous-material suits, firefighters were unable to locate a leak.

As a precautionary measure, five other people were taken to UVRMC for blood tests and released. Police closed off 2230 North from 200 West to about 400 West while firefighters searched for the spill.