Powder found on MBTA bus was chalk

Authorities cordoned off an area around Haymarket Square when a powder, which turned out to be chalk, was found on a bus. (GEORGE RIZER/GLOBE STAFF)

A white powder on the dashboard of an MBTA bus that caused a scare early yesterday in Haymarket Square was common chalk, officials said.

The substance was analyzed at the State Police laboratory, said Joe Pesaturo, an MBTA spokesman. The driver was released from Boston Medical Center after being treated for eye irritation and light-headedness.

"This substance is likely not responsible for the symptoms reported by the bus operator," Pesaturo said in an e-mail.

The driver had been on the road since 5 a.m. and noticed the powder on the dashboard at 9:16 a.m. as she pulled into Haymarket Square, officials said. MBTA Transit Police and fire officials immediately cordoned off Surface Road, and a hazardous materials team responded to the bus station near Government Center.

The name of the driver was not released, but officials said she has worked for the MBTA for 23 years.

"Because of the powder and the symptoms, we decided to err on the side of caution," Lieutenant David Albanese of the Transit Police said.

The bus had been on Route 111, which extended from Broadway in Revere through Chelsea and over the Tobin Bridge. Bus service was disrupted for an hour while traffic was diverted away from the station. There was no impact on subway service, officials said.