The government said it might never find the cause of thousands of crab deaths, but the Dredging of the Tees River has continued after the government said it might never find the cause of thousands of crab deaths.
Campaigners had said they believed the dredging, which restarted on Monday as part of the next phase of work, had released a chemical toxic to shellfish.
The Local Democracy Reporting Service said that the science was very clear as to what didn't cause it, including ruling out the first phase of dredging which ended in November.
We've supported those people who say we need to find out what caused the die-off, and at the moment the most likely working theory is that it could be a foreign pathogen or a disease that caused that, he said.
We have a very strong set of data and science that shows what didn't cause it, although we may not know what caused it.
That allows us to get on with the jobs we said we were going to deliver. The building of the Teesside Freeport is a key policy for the Conservative elected mayor and is intended to bring thousands of jobs to the area.
Houchen, who claimed all conditions had been met, said dredging had been found to be safe and would continue to allow the safe passage of ships across the world.
The second phase of dredging will see a million cubic metres of non-contaminated material deposited about seven nautical miles at sea.
Adrian Noble, a fellow fishermen, said he feared for the future if the cause of the devastating deaths was not identified and resolved quickly.
Responding, Mr Spencer said there had been a shared desire to try and establish the cause, but he said it was very difficult to identify exactly what is the cause, because science works, and that it is sometimes very hard to identify exactly what is the cause.