Workers said they saw up to 40 casualties being taken away on Monday, but the toll could not be confirmed.
"At least five people were killed on the spot and some died in hospital, but we don't know how many," said an official of Naboodah Contracting Co, the main contractor at the site. He spoke on condition of anonymity.
A large partition in a building under construction collapsed, the contractor said. About 150 workers were on site when the partition fell at 0700 GMT.
"The wall fell down and we all ran to help, but there wasn't anything we could do," said worker Daljinder Singh. "Rescue teams were very late in coming. It took them maybe one hour to arrive."
"I saw many, many of my colleagues being taken away," another worker said, before he was told to be quiet by a supervisor. Other workers put the casualties at about 40, saying most were injured. They spoke on condition of anonymity.
The state-run United Arab Emirates news agency said the building site was part of a $4.1 billion expansion project for Dubai airport, one of the busiest in the Middle East. The project is due for completion in 2006.
The project includes a new terminal (Terminal 3), which when completed will raise the number of passengers handled by the airport to 46 million a year.
"Rescue teams were very late in coming. It took them maybe one hour to arrive"
Construction site worker
The design consultant for the Terminal 3 construction is Aeroports de Paris International (ADP), according to the airport's official website. The French firm also operates Charles de Gaulle airport in Paris, where part of a terminal collapsed in May, killing four people.
But an Aeroports de Paris official in France told Aljazeera.net the firm was not involved in the construction where Monday's accident occurred. "We were involved in different sections of the expansion but not the part that collapsed," said ADP's spokesperson.
"The part that collapsed was handled by a British company not us," he told Aljazeera.net.