A soldier wearing a helmet and military fatigues and equipped with a scuba tank descended into one of the mine shafts in a metal cage on Wednesday, emerging minutes later visibly wet.

The rescue team made four attempts to explore the crudely constructed El Pinabete mine in the northern state of Coahuila, but debris prevented them from entering the gallery, officials said.

"They found that they don't have room to move forward. There are obstructions," Defense Minister Luis Cresensio Sandoval said.

Rescuers would keep trying to gain access, the general told reporters in Mexico City.

Five workers managed to escape in the initial aftermath of the accident on August 3, but there has been no contact with the others.

Two underwater drones have been deployed in the operation in Agujita, as have hundreds of soldiers and other rescuers, 25 water pumps and seven drills.

According to authorities, the flood occurred as miners were carrying out excavation work and hit an adjoining mine full of water.

The focus so far has been on pumping out water from the 60-meter (200-feet) deep mine.

The water in the shafts had fallen significantly, from more than 30 meters, but was still several meters deep, authorities said.

"We will be evaluating it throughout the day. We have to be careful not to endanger anyone," civil defense national coordinator Laura Velazquez said.

- Families waiting -

The government's announcement on Wednesday that rescuers were close to entering the mine was greeted with caution by anxious relatives.

"Let's hope that now it's true. Every day they say the same thing," said Juan Orlando Mireles, whose father is among the missing.

Five days ago, soldiers cordoned off the rescue area from journalists and relatives. From behind the fence, it was difficult to observe the rescuers' actions.

In a region facing a severe drought, the amount of water pumped out of the mine over the past week has come as a surprise.

Mireles, a miner like his father, said it could be due to the proximity of the Sabinas River and the old Las Conchas mine, abandoned more than 30 years ago, where a huge amount of water could have accumulated.

Unlike small artisanal mines such as the one where the accident occurred, industrial mines like Las Conchas have long subterranean tunnels where water can build up, he said. They also tend to have reinforced walls, unlike the smaller mines.

Prosecutors have announced an investigation into the accident, the likes of which are common in the state.

Coahuila, Mexico's main coal-producing region, has seen a series of fatal mining incidents over the years.

The worst was an explosion that claimed 65 lives at the Pasta de Conchos mine in 2006.

Last year, seven miners died when they were trapped in the region.