TEXAS CITY, Texas — No timetable has been set to reopen a major U.S. shipping channel after nearly 170,000 gallons of tar-like oil spilled into the Texas waterway, but more help was being called in Monday to contain the spill and protect important shorebird habitat.

A barge carrying about 900,000 gallons of the heavy oil collided with a ship Saturday in the busy Houston Ship Channel, spilling as much as a fifth of its cargo into one of the world’s busiest waterways for moving petrochemicals, according to the Coast Guard.