Traffic was backed up around Exit 24 of the Thruway this afternoon after a gas and diesel tanker caught fire just past the westbound entrance ramp. State Police got the call around 3:45 p.m. No flames could be seen a half hour after the first report, Sgt. Thomas Burroughs reported. Onlookers gathered at a nearby overpass and on the roadway, State Police said. No injuries were immediately reported.