The effort to place a massive containment dome over a gushing underwater wellhead in the Gulf of Mexico was dealt a setback when a large volume of hydrates — icelike crystals that form when gas combines with water — accumulated inside the vessel, a BP official said Saturday.

The dome was moved off to the side of the wellhead and is resting on the seabed while crews work to overcome the challenge, a process expected to take at least two days, BP’s chief operations officer Doug Suttles said.

Suttles declined to call it a failed operation but said “What we attempted to do last night didn’t work.”

Suttles said the gas hydrates are lighter than water and, as a result, made the dome buoyant. The crystals also blocked the top of the dome, which would prevent oil from being funneled up to a drill ship.

“We did anticipate hydrates being a problem, but not this significant [of one],” he said.

Two options officials are looking at to resolve the problem are heating the dome or adding methanol to dissolve the hydrates, Suttles said, adding that they are continuing to assess other methods to capturing the oil.

The crude is leaking at a rate of 210,000 gallons (5,000 barrels) a day.

Suttles said that another possible solution would be to “take ground-up material of various types and try to inject it into the blowout preventer at the bottom of it and it will flow up and plug it up,” an operation he compared to stopping up a toilet.

(Read More: CNN)