MOSUL DAM, Iraq (AP) — A team of Italian specialists arrived Thursday at the site of the Mosul Dam as part of an emergency campaign to repair Iraq's largest dam before it collapses.

The advance team from the Italian engineering firm Trevi Group will set up a camp for the group of engineers who are expected to arrive within a few weeks.

U.S. and Iraqi officials have repeatedly warned that the dam is in imminent danger of collapse.

In late February, the U.S. embassy in Baghdad called the dam's risk of collapse "serious and unprecedented," and Prime Minister Haidar al-Abadi asked Mosul residents along the Tigris river to move at least six kilometers (3.7 miles) away from its banks.

The dam's core problem is that it was shoddily built on unstable ground: The earth underneath it is constantly being eroded by water. From the day it was inaugurated in 1985, maintenance crews have had to continuously pour cement under its foundation.

Without that constant injection — known as "grouting" — the 113-meter-high dam would soon collapse into a hole in the ground, causing an unprecedented disaster. The 30-mile long lake behind it would explode down the Tigris River valley with hundreds of millions of cubic meters of water, ramming into Iraq's second-largest city, Mosul, currently home to more than 700,000 people about 40 miles downriver. It would then flood all the way down to Baghdad, some 340 miles south.

U.S. officials have estimated more than a half million people could be killed. Millions more would be driven from their homes.

Things have worsened because the dam was captured for several weeks in 2014 by the Islamic State group. U.S.-backed Iraqi forces retook the dam, but no grouting took place for six weeks. Even since then, the grouting has not been up to full levels in part because the militants control the nearby factory that produces the concrete for the dam.

As a result, there are "almost certainly ... an unprecedented level of untreated voids" in the dam's foundation from continuing erosion, the U.S. Army Corps of Engineers said in a Jan. 30 report.