A Nigerian dockers' union said on Thursday it had ordered a strike at Lagos' Apapa port after three men died, bringing the port to a standstill when it is struggling to clear the worst congestion for 25 years. The Maritime Workers Union of Nigeria (MWUN) said it had asked its members to stop work following an incident in which three men died after inhaling poisonous fumes on Wednesday. "We received a report yesterday that two of our members died at the Apapa port after inhaling dangerous gas while working on a vessel," union officer Tony Anyanwu said. "We have sent our men out to the port to investigate what actually happened," Anyanwu said, adding that the vessel was the MV Marina Bay." Nigerian Ports Authority (NPA) spokesman Babatunde Sanni said he was not aware of the deaths or any walkout by workers. Another Nigerian Ports Authority (NPA) official said that accidents used to be common but Apapa's safety record this year had been exceptionally good. "This is a commercial place and you always have these kinds of deaths," said an official who asked not to be named. "It may have been an accident. All we can do is to advise people to be more careful while working out there." The container terminals at the Apapa and Tin Can main ports are overflowing with cargo with containers filling every available space, ports officials said. The severe congestion on the quayside and within the ports has been blamed on a new customs policy introduced in April requiring a thorough inspection of every item brought into Nigeria. The European Community Shipowners Association (ECSA) representing French, British, Belgian and Dutch companies who are losing money as the crisis drags on, have threatened to impose extra charges on Nigeria-bound ships. The congestion has put a severe strain on the entire economy of West Africa. Neighboring countries including Benin, Cameroon, Niger, Ghana and Ivory Coast depend on Nigerian industries for manufactured goods. As a result, scores of ships waiting to berth were still visible from the shoreline on Thursday, industry sources said. NPA officials would not say how many ships were waiting for berths.