The motorway was closed in both directions between J3A and J4 (Whitburn) at around noon on Saturday as police were called to a “person of concern” with pictures released by Traffic Scotland showing a long tailback of traffic on eastbound carriageway.
Blackburn Road into Bathgate was also closed while officers attended to the incident.
One motorist stuck in the tailback posted on social media: “Currently parked on the #M8 eastbound near Bathgate as its been closed due to a police incident. Avoid at all costs.”
Photographs posted on Twitter showed drivers leaving their stationary cars as the tailbacks continued.
Around 3.35pm, as traffic started to move slowly once again, misery for motorists continued as the M8 shut in both directions to allow an air ambulance to attend a five-vehicle crash on the eastbound carriageway between J4A and J4.
The westbound carriageway opened at around 5pm, while the road fully re-opened at 9.15pm on Saturday night.