SEATTLE – Hazardous materials teams ordered the shut down of all northbound lanes of I-5 in Seattle near the I-90 interchange for over two hours Wednesday afternoon when a tanker truck began leaking toxic material.

Some lanes of traffic finally reopened just before 3:20 p.m.

Troopers were called to the scene initially as a report of a disabled tanker on the onramp to I-90 just after 1 p.m., but when troopers arrived, they discovered the spill, Seattle fire officials said.

Originally, Seattle fire officials estimated 50 gallons of sodium borohydride had leaked from the tanker. But later, officials revised the estimate to just two gallons. The leaking substance is used to bleach wood and is quite toxic, fire officials said.

Crews kept everyone at least 300 feet back from the tanker as hazmat teams worked to contain and clean up the spill.

At the peak of the incident, the backup stretched for several miles. There is no word what caused the leak.