Mr Toy warned people to stay away from the park until further notice. This also includes whitebaiters using the Matarawa Stream, as it may be contaminated with sewage.
He said the situation would be reviewed today.
Meanwhile, flooding fears caused by the rising Whanganui River proved to be unfounded.
Wanganui District Council's emergency manager Max Benseman said staff monitored the river over the weekend after heavy rain on Friday. Mr Benseman initially warned the river could rise to 9m, but he said less rain fell than was forecast.
"The Whanganui River peaked at 6.2m ... There are no concerns now about river levels or flooding," Mr Benseman said.
The weekend's strong winds are set to continue this week, with gusty north-westerlies forecast along with a few showers.