“Two of the seven suspects are employees of PT Freeport Indonesia,” National Police spokesman Nanan Soekarna told the Jakarta Globe. He identified the two employees as Amon Yawame and Dominikus Beanal.

“We are still investigating what roles they played,” he said, adding that some of the suspects would be charged with murder.

A series of attacks on Freeport’s vehicle convoys in Timika, Papua, have killed at least three people since July 11.

The latest incident took place last Friday, when a convoy of Freeport vehicles came under attack, leaving a police officer and a local Freeport employee with gunshot wounds.

On July 11, Australian national Drew Nicholas Grant, a 29-year old project manager at Freeport, was killed when the vehicle he was in was attacked. The next morning, an Indonesian security guard was killed in another ambush. A police Mobile Brigade officer who went missing on July 12 during a third attack was found dead the day after in a ravine near the ambush site.

Police have arrested at least 15 people in relation to the incidents, which have also injured at least 13 people.

Meanwhile, thousands of Freeport employees forced to stay at the mining site since July 11 due to security considerations were finally able to go home on Sunday.

“We have not taken a day off for three weeks and are grateful that we are back safe and sound,” one worker said.

The National Commission on Human Rights (Komnas HAM)said the attacks were carried out by “well-trained and professional” individuals who had the skills to manage to get past tight security at the mining site.

“The attacks are clearly the work of well-trained and organized professionals,” said Matius Murif, deputy chairman of the Papua office of Komnas HAM.

“That is why they were able to get past layers of security.”

Imparsial, a prominent rights group, urged the authorities not to point fingers at the separatist Free Papua Movement (OPM).

The group argued that the attacks must have been planned and conducted by trained militants who had experience with weapons and the expertise to get around tight security.

Some analysts have also suggested that the shootings stemmed from a rivalry between the police and the military over multimillion-dollar illegal gold mines, or protection contracts for the mine.

The Indonesian Armed Forces (TNI) were in charge of security around the mining site until 2004, when a presidential decree on the protection of vital interests was issued.

This decree put the security of important sites such as mines under the protection of the National Police.

Papua is home to a four-decade-old, low-level insurgency.

Members of OPM, who see Freeport as a symbol of outside rule, were initially blamed by authorities for the latest violence in the province.