RIO DE JANEIRO, Jan. 16 -- A succession of human errors caused the plane crash that killed Brazilian presidential candidate Eduardo Campos and six others last year, O Estado de Sao Paulo daily reported Friday.

An air force investigation concluded that pilot Marcos Martins lacked training for flying that particular aircraft, a Cessna 560 XL, and made several mistakes that led to the August 2014 crash, according to the daily.

The official conclusions are yet to be released.

The accident took place on a rainy day with low visibility. The poor weather and state of the runway were also contributing factors, the paper quoted investigators as saying, though they placed most of the blame on the pilot.

There was no evidence of mechanical failure and no other evidence was available as the flight recorder had not been turned on, said the paper.

Campos' brother Antonio Campos questioned the daily's story, noting that such investigations, as a rule, offer possible causes, not conclusions. He said the investigation was not expected to be completed until next month, and called the daily's decision to publish the report premature.

The paper said Martins apparently disregarded recommended landing guidelines for the local airport in Santos, Sao Paulo state, which has a short runway considered challenging even by experienced pilots, and failed to land on his first try.

During a second attempt, he suffered from a "spatial disorientation," the paper quoted investigators as saying. That explained why he descended at a 70-degree angle at full speed. The pilot thought he was pulling up, instead of heading down, said the paper.

Martins had posted that he was very tired on social media several days ahead of the accident and he had a poor relationship with his co-pilot, who had asked not to be partnered with him, the paper said.

The pilot and co-pilot, and four of Campos' campaign assistants also died in the crash.

Campos' death disrupted Brazil's presidential campaign, forcing the opposition to find a new candidate, only two months before election day. Enditem