Police tight-lipped on Geraldton boat

Authorities are remaining tight-lipped about an investigation into a suspicious vessel that docked at Geraldton on WA's Mid West coast.

Firemen wearing protective suits boarded the boat on Tuesday and removed items contained in secure bins, but federal police would only say Commonwealth and state agencies were working on the matter.

"As operational activity is ongoing it would not be appropriate to comment further," a spokeswoman said.

An Australian Border Force spokeswoman told AAP on Monday the boat was not an irregular maritime arrival.