Nearly 700 dead rats found on a West Coast beach didn't die of 1080 poisoning.

Westport residents were horrified when hordes of dead rodents washed up on popular North Beach almost two weeks ago.

Some of the hundreds of rats - and a dead weka - were tested by DOC for toxins after concern they could've been killed by a recent 1080 drop.

But West Coast Operations Director Mark Davies says none of the animals showed any traces of 1080 - and the cause of death couldn't be determined.

• Hundreds of dead rats wash up on Westport beach