A late-night rescue has been undertaken after a trio of cavers ran into trouble near Nelson.

Sergeant Matt Elliott said police received a call from three men in a cave at the Riwaka Resurgence, near Motueka, about 10.15pm.

One of the men had become trapped and four search and rescue staff were sent out to help him, Mr Elliott said.

The man was freed after about one-and-a-half hours. No injuries were reported.