Traffic was snarled on the Tobin Bridge early Monday morning due to a semi truck that lost its trailer.

It happened around 6:20 a.m. on the southbound lanes of Route 1, along the Tobin Bridge, in Boston.

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According to MassLive.com, all but one lane on the highway were closed due to the incident. The incident caused bumper to bumper traffic, with traffic moving at an average of 6 miles per hour in the area.

Kristin Eck from WBZ NewsRadio tweeted this aerial photo from the scene.

It’s unclear what caused the trailer to disconnect from the tractor. The incident has since been cleared.