Update at 7:20 p.m. — As of 6:45 p.m., all lanes on I-66 have reopened.

A tractor trailer fire in Fairfax County may tie up rush hour traffic on I-66 this evening.

A truck carrying hay caught fire near Route 123 this afternoon. The hay quickly became fully-engulfed, leaving a smoldering mess that forced authorities to close all westbound lanes of I-66. At least two Bobcat front loaders have been brought in to help with the firefighting and clean-up efforts.

Backups on westbound I-66 now extend to the Beltway. The backups may worsen as rush hour approaches. Cars have been spotted crossing the median on I-66 in an attempt to get out of the miles-long traffic jam.

Westbound Route 50, a possible alternate route, is also backed up to the Beltway.

Photo courtesy @DavidLyonHall