But the black commemorative plaque listing 40 victims of Islamist militants there keeps the memory alive of the January attack that shook investors' faith in Algeria's oil and gas sector.

Officials at the Tiguentourine gas plant in Amenas point to tighter security, a new helicopter landing pad to allow safer transport and a permanent military presence.

"Helicopters patrol the area, and military are everywhere all around the site, even if they are not visible to you," an Algerian official said.

But Algeria has joined neighbouring Libya and Egypt, both caught up in political upheaval, as a tough sell to foreign energy firms. The region's cost to reward ratios is less appealing than elsewhere and Islamist militants threaten more attacks across North Africa.

The Maghreb has been shaken by instability since the 2011 Arab Spring revolts. Islamist militants tied to al Qaeda have gained ground, especially in the chaos of post-revolution Libya.

The Amenas attack was a surprise for Algeria, a top gas supplier to Europe, an oil-producing OPEC member and a U.S. ally in the fight against al Qaeda. Its security forces have years of experience battling Islamist militants.

A senior Algerian official at Amenas said the new security plan had been discussed with executives from BP and Statoil, partners in the plant, who said they need guarantees and a reinforced security presence before workers return.

The Norwegian company released a report last month saying it had missed a string of warning signs prior to the attack. The British oil major has said it was impossible to predict the attack.

The British ambassador to Algiers said in September that BP workers could return soon, without giving details. The company has said it would only support the return of contractors "if and when" it is satisfied with security.

Military presence

During a recent visit to the site, a couple of soldiers and a policeman were visible, and a light tank was posted in the entry gate. Algerian workers using bicycles moved around the plant wearing blue uniforms.

To reach the gas facility, visitors must pass through three military checkpoints, then to access the site visitors must wait for an escort, and finally get identification before entry.

The senior Algerian official said a new helicopter landing facility would allow foreign workers to fly into the site instead of making the 50 km drive from nearby In Amenas airport.

"The landing facility will be inaugurated in November, and we expect foreign workers to be back before the end of this year, likely in December," one official said asking his name not be used because he was unauthorised to speak to the press.

More than 800 Algerians work on the site now. Some 120 foreigners used to work at Tiguentourine's gas plant.

"We will never forget what happened, the faces of my foreign colleagues still haunt me," said one source. "We believe that around 50 foreign workers will be back before the end of this year."

Algerian gas workers were keen to show how they had succeeded to bring back gas production without the assistance of their foreign colleagues.

"We are currently producing 16 million cubic meters per day but we will go up to 25 mln next month after a maintenance period ends," a facility official told Reuters.

He said only two of the plant's four trains are currently working.

Gas burning is visible, evidence the plant is back to business, say workers.

"Executives who visited the site after the attack were impressed by the job done by the Algerian technicians, who fixed the damage and resumed production," the source said. "That was a challenge. But now we need our foreign colleagues to come back because we are partners here."