An 18-wheeler rolled over Thursday afternoon on the ramp from Interstate 35 South to Interstate 10 West, spilling its cargo.

Traffic leaving downtown backed up on that interchange almost immediately as crews began working to clear the wreck.

According to San Antonio police, the big rig was carrying 18,000 pounds of lumber. It is still not yet known what caused the accident.

San Antonio firefighters dumped absorbent material on some spilled fuel and then emptied out what was left in the fuel tank.

As of 4 p.m. on Thursday, a San Antonio police spokesman said the following lanes were closed:

  • 35 South to IH 10 W
  • 35 NB and SB to IH 10 W
  • IH 10 W entrance ramp @ Elmira
  • All lane shut down to IH 10 W
  • Blocked NB entrance ramp from Cesar Chavez
  • Closed NB 35 to WB IH 10 W

There has been no word about when the mess will be cleared.