BOSTON -- MBTA police spotted what they called a "suspicious" package on an elevated structure above the Sullivan Square MBTA station early Wednesday morning and shut down Interstate 93 in both directions until they could determine what the package was.

The State Police bomb squad was called and detonated the package just before 10 a.m. The highway was reopened shortly after.

Officials said the package contained an electronic circuit board with some components that were "consistent with an improvised explosive device," but they said it had no explosives.

They determined that the device was not dangerous, but destroyed it as a precaution.

"We determined that this device, in particular, was not explosive," said MBTA Lt. Sal Venturelli.

He said 'T' police were told about the package by a transit passenger who spotted it on a column that supports Interstate 93. The parcel was located on an elevated structure above the busway and below I-93 in the Charlestown section of Boston at about 8 a.m.

"This is a perfect example of our passengers taking part in Homeland Security," Venturelli said.

An investigation will be conducted into how the package got there and when, he said.

Train service on the Orange Line between Sullivan Square and Wellington stations was suspended in both directions. No injuries were reported.

The northbound side of I-93 was closed, causing significant traffic backups. Motorists were not allowed to access the highway near Sullivan Square coming up from the south.