A port worker has died as coal was being loaded on a ship at Lyttelton this morning. 

The death is the second at New Zealand's ports over the past week. 

The person killed this morning worked for the Lyttelton Port Company, the firm's acting chief executive confirmed to the NZ Herald. 

"Sadly an LPC staff member has passed away while the vessel was being loaded with coal for export," said Kirstie Gardener. 

"At the moment we can't confirm any further details on the incident. I wish to express my deep sadness and condolences to both the family of our team member and to the rest of the LPC team. 

"Our focus right now is on supporting our staff and the family of our LPC team member at this tragic time." 

Maritime New Zealand, which extended its "heartfelt" condolences to the victim, is investigating the accident. 

Maritime New Zealand Principal Communication Adviser Vince Cholewa said investigators will carry out interviews, examine the scene, review documents and gather evidence as required. 

"Maritime New Zealand will assess all the information gathered, then make a decision about what, if any, further action to take." 

Calling the death a "tragedy", Council of Trade Unions president Richard Wagstaff said there is an "urgent need" for an inquiry into port safety. 

"The Maritime Union of New Zealand, Rail and Maritime Transport Union and New Zealand Merchant Service Guild have called for an inquiry into port safety, from which national standards would be developed. The New Zealand Council of Trade Unions wholeheartedly endorses these necessary measures." 

Wagstaff said the death came just three days before Workers Memorial Day. 

"Every worker deserves to know that when they go to work in the morning, that they will be coming home safely at the end of the day. Sadly that is currently not the case in this industry, and urgent action is needed," he said. 

Eight people, a number in high visibility vests, have arrived at the docked vessel since 11am. Three have since gone on board. A small number of Lyttelton residents and port workers have visited a lookout overlooking the scene. 

The fire service's Andrew Norris said crews were on board a coal-carrying vessel called the ETG Aquarius at Lyttelton this morning where a person had been injured. 

Norris said two fire appliances from Lyttelton, one from the central city and one from Woolston had attended the incident. 

A St John spokesperson said one ambulance, a manager and an intensive care paramedic responded to the incident around 9.12am. 

"Police are assisting ambulance with an incident at Cashin Quay, Lyttelton that was reported shortly before 9.30am," a police spokesperson said. 

Otara resident Atiroa Tuaiti died shortly after 9am last Tuesday following a "fall from height" while working on a Singaporean container ship docked at Ports of Auckland. 

Tuaiti grew up on Aitutaki in the Cook Islands, but moved to South Auckland during his teens and attended Mt Roskill Grammar. It is understood he had worked at the port for several years. 

He welcomed his first son in October last year, and relatives have told the Herald of their grief for his utterly "heartbroken" partner, Kura.