Day four wound down Tuesday (Fiji time) with 74 teams spread across the better part of Fiji's main island of Viti Levu. The USA's Team Montrail/Parallax is nearly two hours ahead of a surging Team Buff AXN and a steadily moving Team Spie of France.

While most teams continued their mountain bike leg to CP4 and subsequent inflatable kayak section to CP5, five lead teams cleared CP6 after an arduous 20-hour trek toward the northern part of the island, locating two more tikis on the "Trail of Fire."

At 8 a.m. Tuesday, Montrail arrived at CP6, a two-hour fixed-rope climb up hundreds of feet of waterfall and slippery rock. No one was able to access the area due to weather conditions today, but we'll catch up with teams there on Wednesday, and file photos as soon as we're extracted back to a telephone line.

And so Tuesday was spent back at the beautiful Mbegga area where teams passed each other across the river, as we caught up with a big cava ceremony - and more teams in the middle and rear of the field. Meanwhile the top 10 teams raced for the Vuwa Falls of CP6. While the race remains somewhat on the timetable organizers expected, anything can happen at this point, as the lead teams are now headed into the toughest navigation section of the race.

"Between CP6 and 7 is the navigational crux of the course," Mark Burnett told MountainZone.com. "It's very confusing, and the second pack of teams has a chance to catch the leaders if those lead teams implode [from the pace they're setting]. This year especially, it's not over until it's over."

Night fell with locals informing race organizers that a red flare had been spotted arcing into the night sky, but Burnett said there was nothing they could do about it until morning.

"The course is as challenging as we predicted," he said. One team from Panama, BellSouth Panama, had been missing for 35 hours before finally being located Tuesday, just one hour from the time at which organizers would have instituted a search and rescue effort.

Another team, 6th-place Air Pacific of Australia, hadn't checked into CP6 at press time, also concerning Burnett. "Hopefully they found a place to sleep, we'll find out tomorrow. But they're down to 11th place at best at this point." Added to the injuries and bad luck of teams like Team GoLite and Schick Xtreme, the navigation difficulties have made for an exciting and harrowing race thus far. And the lead teams aren't expected to finish for at least another three days.

One team doing great at this point is Spain's Buff AXN, which surged to 2nd place just minutes ahead of Spie. "I've seen Spain do almost clairvoyant navigating," said Burnett. "They're really good on land, but we can't write off Spie either." Burnett said he's also very happy with the performances of the rookie South Africans, Team Mazda, currently in 5th place and Canadian Team Running Free, now in 14th place.

There is plenty of action at the back of the race too. Any teams hoping to continue must clear the kayak checkpoint 5 by 1 p.m. Wednesday, or face being disqualified. The teams spotted on the river Tuesday looked to be in good spirits, with a few exceptions, such as a member of 64th-placed Team Visit Argentina who seemed on the verge of collapse.

Another USA team, Team Lupus Foundation, plugged along in 69th place after struggles within the team. Team captain Maurice Nelson is hoping to become the first African-American to complete an Eco-Challenge.

Other teams, such as 70th-placed NYST (New York State Troopers) simply rested next to the river, even taking time to wash up before continuing on. The team had been prepared to race in last year's New Zealand event, but were unable to due to 9/11, just a month before the race.

Also spotted on the course, in 58th place, were two members of the Smirnoff Ice Playboy X-treme team, looking fresh as they rested in the shade and waited for a teammate who had bike problems. "I've got all sorts of weird bumps or some sort of heat rash," said one of the women as she took a drink and rested.

Next up for lead teams: Trekking and pack rafting, followed by more mountain biking after CP8.

—Ari Cheren, MountainZone.com Correspondent