Two years after 102 people died in Greece's worst fire tragedy, a judicial probe into operational errors has been rocked by cover-up claims, while reconstruction remains a distant goal.

Wildfires fed by strong winds swept through homes and vehicles in the coastal town of Mati near Athens in July 2018, leaving only charred remains.

The Kathimerini daily reported last weekend that Dimitris Liotsios, a fire department investigator probing the disaster, was allegedly told by his chief officer to "bury" and "doctor" files under "top-level" orders.

Liotsios used his phone to secretly record the meeting with then fire chief Vassilis Mattheopoulos and submitted it to judicial authorities, the newspaper said.

According to Kathimerini, Mattheopoulos told the investigator to "keep your mouth shut" in order to avoid retaliation by superiors at the fire department and the police ministry.

"If you write about your superiors having any blame, we will close ranks and tear you apart," the fire chief allegedly said.

Prime Minister Kyriakos Mitsotakis has called the report "chilling".

"It is now clear there was an attempted cover-up," the premier said Sunday.

At the time, the left-wing government of then prime minister Alexis Tsipras had stressed the difficulty of organising an evacuation in the coastal community with winds blowing at nearly 120 kilometres an hour (75 mph).

Some locals reported suffering burns from the scorching wind without ever coming near the fire.

But in the aftermath of the disaster, the police and fire services gave conflicting accounts of what went wrong.

Local residents received no warning about the proximity of the danger, and instead of being sent away from the fire zone, many motorists were mistakenly diverted into its path and died trapped in Mati's narrow streets.

Four senior officials, including the minister responsible for the police, later resigned or were removed from their posts.

Police and fire services gave conflicting accounts of what went wrong. The picture shows a memorial service a week after the fire
Police and fire services gave conflicting accounts of what went wrong. The picture shows a memorial service a week after the fire AFP / LOUISA GOULIAMAKI

An Athens magistrate is finalising charges against 20 people including the regional governor, local mayors and senior fire service and police officials. Citizens have also filed separate lawsuits.

The first defendant, former Marathon mayor Ilias Psinakis, is to testify on Friday.

The police minister at the time of the cover-up claims, Olga Gerovassili, denies any interference in the case.

"I took over on August 29... This discussion seems to have taken place towards the end of September. I had not even met (these officers)," she told Skai TV this week.

Former fire chief Mattheopoulos has also dismissed the report as "lies", denying any contact with the investigator.

"There was no meeting or contact... He did his job, I did mine," Mattheopoulos told state television ERT over the weekend.

Kathimerini executive editor Alexis Papachelas said Sunday it was "frightening and outrageous" that "cynical beasts" were given key roles during the tragedy.

A memorial service for the victims was held on Sunday.

Evangelos Bournous, mayor of Rafina, the town with administrative responsibility for Mati, estimates that reconstruction will take another two years.

"Obviously the process is slower than municipal authorities and residents would want. More than half the residents are still displaced," he told ERT.

But rebuilding the entire community under new urban planning and safety rules takes time, he said.

After the tragedy, officials found that years of illegal construction in Mati had cut off access to roads that could have helped more people escape.

The environment ministry now plans to demolish some 140 homes and 340 enclosure walls in the area, a move opposed by many residents.

The plans go beyond ensuring fire safety.

"I saw several homes built in a creek bed," Environment Minister Costis Hatzidakis said during a visit earlier this month.

"If there is a flood here tomorrow, there will be mayhem."