MAE SAI, Thailand (AP) — The frantic effort to locate 12 boys and their soccer coach missing in a cave in Thailand for a week picked up pace as a break in the rain eased flooding in the system of caverns and more experts from around the world joined the anxious rescue mission.

The search in the northern province of Chiang Rai has been going slowly, largely because flooding has blocked rescuers from going through chambers to get deeper into the cave. Pumping out water hasn't solved the problem, so the attention has focused on finding shafts on the mountainside that might serve as a back door to the blocked-off areas where the missing may be sheltering.

The boys, aged 11 to 16, and their 25-year-old coach entered the sprawling Tham Luang Nang Non cave after a soccer game on June 23, but near-constant rains have thwarted the search for them. Authorities have nevertheless expressed hope that the group has found a dry place within the cave to wait.

Reflecting that hope, a medical evacuation drill was held Saturday morning to see how long it would take to get rescued people out of the cave into 13 ambulances and to the nearest hospital.

Australian police and military personnel joined other multinational teams, including U.S. military personnel and experts from a British cave exploration club. China sent a six-person team of rescue and disaster experts to the cave, the Chinese Embassy in Bangkok said. The group has experience in lifesaving operations in Myanmar and Nepal, the embassy said.

A second, private Chinese group calling itself Green Boat Emergency also arrived Saturday. "Our skills are search-and-rescue on mountains and in caves. We hope we can help," said Wang Xudong, a member of the group.

Chiang Rai Gov. Narongsak Osatanakorn said the falling water level in the cave has helped the rescue effort considerably.

"Today, the situation is much better and we have high hopes, and will be here all night," he said early Saturday evening.

Thai navy SEAL divers have been crucial to the search, but have been stymied by muddy water reaching the cave's ceiling, forcing them to suspend operations again and again. With water levels dropping, they resumed dives Saturday, re-entering a chamber from which they had retreated earlier in the week. But they could not advance farther than 200 meters (yards) from their current position, the team reported.

In addition to pumping out the flooded chambers, rescuers were working on finding the source of the water that's been rushing into the cave in order to drain or divert it.

Chaiwat Dusadeepanich of the Department of Groundwater Resources said that his team, which has been drilling for two days, found a small underground water source near the cave.

"But the water flow rate isn't great enough," he said. "We would have to drill in deeper to get to the source, but at least we found it. Hopefully we can start pumping out the well water by the end of today."

Hopes were also high for finding some kind of access through fissures on the mountainside that might lead to shafts into the cave.

"Yesterday our team climbed into one shaft, and went in around 50 meters (yards)," said National Deputy Police Chief Wirachai Songmetta. He said the shaft had led to two separate chambers so far, and they planned to re-enter the second one in a bid to find passages that could lead to other chambers, Wirachai said.

Officials also began dropping care packages into the shafts in hopes the missing might retrieve them. Each package contains food, beverages, a phone, a flashlight, candles, a lighter and a map of the cave.

___

Associated Press video journalist Jason Corben in Bangkok contributed to this report.

Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.