Authorities said Thursday that a busy stretch of an interstate highway in New Jersey was shuttered after a swath of the right lane and a shoulder collapsed into a sinkhole.

The New Jersey Department of Transportation confirmed the sinkhole Thursday morning near the Wharton exit on Interstate 80 eastbound, which is about 40 miles west of New York City.

The depression formed off the shoulder and right lane, according to NJDOT, and it stretches 40 feet wide and 40 feet deep. The transportation department said all lanes of I-80 eastbound were closed and being detoured with motorists advised to avoid the area and seek alternate routes. The cause of the sinkhole has not yet been determined.

“NJDOT crews responded immediately and are on site continuing to evaluate the situation, determine the extent of the damage, and stabilize the area in order to design a repair,” NJDOT officials said.

Westbound I-80 is not impacted. A 511nj.org live feed of I-80 looking west shortly after 5 p.m. showed traffic moving swiftly on the westbound side with traffic cones lined up and several emergency vehicles on the eastbound side. A line of traffic appeared to be at a standstill as motorists were waiting to take Exit 34.

A sinkhole is a hole or deep depression in the ground that opens up when layers of certain types of rock – usually limestone, carbonate rock and salt beds – dissolve beneath the surface and collapse.

Sinkholes usually form over time by a phenomenon called karst processes in which groundwater breaks down minerals in the underlying soluble rock. The dissolved minerals create spaces inside the rock, weakening it until it collapses.