A local employee was shot dead in the ambush, which resulted in the abduction of three Australians, two Nigerians, a New Zealander and a South African.
"We are working to ensure the safe return of all the men involved and are in communication with their families," the company said in a brief statement this afternoon.
"Macmahon is providing support to the men's families and we ask the media to respect their privacy at this time."
Earlier today, Prime Minister Malcolm Turnbull said the Australia High Commissioner was on the scene working with local authorities to secure the men's release.
He urged the media to be restrained in their reporting due to the sensitive nature of the situation.
"But it is a very serious kidnapping, a very serious criminal assault," he said.
"One person was killed as you know and the seven people have been kidnapped."
Macmahon said counselling had been made available for all employees and their families.
Shares in Macmahon remain in a trading halt.
The Perth-based contractor has a 6.5-year, $US105 million contract to perform all limestone mining activities at Lafarge's Ewekoro cement plant in Nigeria.
Orica CEO Alberto Calderon told reporters in Perth this afternoon that he felt for the people at Macmahon.
"Nigeria may be one of the most difficult countries to operate in," he said.
Orica does not have any operations in Nigeria but it is active across the African continent.
"We obviously take a very rigorous approach to our people's safety."
