Four stowaways found on the Italian 71,000-tonne ship Grande Tema in the Thames Estuary threatened its crew and demanded to be taken to the coast, The Sun newspaper reported Saturday.

The ship's crew had to lock themselves in the vessel's bridge for safety, media reports said.

UK Police said they did not think the incident was piracy or terrorism related. "We have received no reports that anyone has been harmed and don’t believe they are at risk. We are not currently treating this as either a hostage, piracy or terror-related incident," Essex Police said, as quoted by The Sun.

According to Reuters, the suspects were believed to have boarded the vessel in Nigeria and had demanded to be taken to the English coast, threatening the Grande Tema's crew with iron bars.

UK police said Saturday that the special operation to regain control of the ship is over, that the vessel has been secured and that four men were detained after the completion of the operation.