4:36 p.m. Update:
The crash has cleared and westbound I-66 has reopened at the Beltway. Expect some delays to linger.
An accident on westbound Interstate 66 is blocking all lanes before the Capital Beltway, according to Fairfax County. Traffic is backed up east of Broad Street/Route 7. Expect major delays and avoid I-66 if you can help it.