KOLONTAR, Hungary – The owners of the metals plant whose reservoir burst, flooding several towns in western Hungary with caustic red sludge, expressed their condolences Sunday to the families of the seven people killed, as well as to those injured — and said they were sorry for not having done so sooner.

MAL Rt., which owns the alumina plant in Ajka, also said it was willing to pay compensation “in proportion to its responsibility” for the damage caused by the deluge.

But the trouble may not be over.

With the northwest corner of the storage pool still showing a hole 50 yards wide where the mix of mud and water broke through last week, officials said the collapse of at least one of the breached walls was inevitable. That, they said, would probably unleash a new deluge of toxic matter that could ooze a half-mile to the north, wreaking further havoc.

That would flood parts of the town nearest the plant — one of those already hit by the industrial waste Oct. 4 — but stop short of the next town to the north.

Environmental State Secretary Zoltan Illes said that recently discovered cracks on the northern wall of the reservoir at the alumina plant have temporarily stopped widening because of favorable weather conditions but will continue to expand, especially at night.

Disaster agency spokesman Tibor Dobson said engineers didn’t detect any new cracks overnight Saturday, and the older cracks were being repaired, but it was too soon to consider lowering the state of alert.

Protective walls were being built around the reservoir’s damaged area to hold back further spills. And a 2,000-foot- long dam that will be between 4 and 5 yards high was under construction to save the areas of the town of Kolontar not directly hit by last week’s toxic flood.

“I would describe the situation as hopeful, but nothing has really changed,” Dobson said. “The wall to protect Kolontar is planned to be finished by tonight, but it will likely be several days before residents may be able to move back.”

Nearly all of Kolontar’s 800 residents were evacuated Saturday, when Prime Minister Viktor Orban said the north wall of the massive storage pool was “very likely” to collapse because cracks had appeared at several points.

The roughly 6,000 residents of neighboring Devecser, just north of Kolontar, were told by police Saturday to pack a single bag and get ready to leave at a moment’s notice.

“This hasn’t changed,” Dobson said. “We are still on guard in case of any more spills.”

Illes said that, since it would be impossible to transfer the 568 million gallons of sludge still in the damaged reservoir anywhere else, he had set a 2-month deadline for closing up the huge opening.