By Mark Doyle
BBC News, central Colombia
Illegal cocaine-producing laboratories are often hidden in the jungle
We reached the river at dawn. It was swollen with recent rain and flowing fast.
But at first I could not see how we were going to cross it - there was no bridge.
I was accompanying the anti-narcotics squad of the Colombian police on a raid against a suspected cocaine-producing lab.
But the lab was on the other side of the swirling brown water.
Some of the elite paramilitary police commandos, known locally as "Los Jungla", or "The Jungle Squad", had already gone across - but how?
It was then that I spotted a thick steel cable strung across the river.
Drums of precursor chemicals are used in the production of cocaine
Slung underneath it, and connected by a pulley system, was a wire basket roughly the size and shape of a large supermarket trolley.
We clambered in and one-by-one slid across the river.
The Jungle Squad, on a point of pride, hauled themselves over personally by gripping the cable with stout gloves.
Some of the other men - and myself - were helped by a police officer on the other side pulling on a rope attached to the basket.
It was a bit like a fairground ride. But there was nothing amusing about what we found hidden in the bamboo trees on the other bank.
First, we found a cache of big 25-gallon drums of chemicals. Some were empty; others had recently been delivered here and were still full.
"These are the precursor chemicals," said Maj Edwin Meneses, the commander of the raid. "They mix these in the process of transforming coca paste into refined cocaine."
Futher up a jungle path, we found the lab itself. It was a complex of filthy, muddy shelters covered with large, black plastic sheets - to keep off the tropical rain and in an attempt to hide from aerial surveillance.
Underneath the sheets were small electricity generators, microwave ovens (used to crystallize the cocaine), fuel - and several football-sized plastic wrappers full of white powder.
The heavily-armed police officers - who looked more like soldiers in green combat fatigues - set to work.
One, a chemist by training, opened his mobile testing bag and started analysing the white powder.
"It's cocaine," he said.
Another found a pistol - long-barreled and silver like the ones seen in westerns - and handed it to Maj Meneses.
A third officer had spotted a couple of mobile phones and they were gathered up too.
What the squad did not capture was any of the workers in this illegal lab. They had run away after seeing the first commandos coming across in the basket.
Anti-narcotics squads haved netted tonnes of drugs and chemicals
I put it to Maj Meneses that this was something of a failure.
"No, the raid was a success," he insisted. "Not only will we destroy this lab but we've gathered a lot of intelligence here which will help us know who was working here and who they are connected with."
The major said this raid was one of "six or seven" which had been mounted recently, netting a total of three tonnes of cocaine and 40 tonnes of precursor chemicals.
According to UN figures, Colombia produced 430 tonnes of cocaine last year. That was down on the previous year.
But the acreage of coca fields under cultivation is estimated by the UN to have been fairly constant over the past five years - so production could rise again unless the programme of crop eradication (by aerial spraying) is continued.
From his on-the-ground perspective, however, Major Meneses was more optimistic.
"We think the strategies are working," he said. "With this raid and others we have seized a large quantity of drugs, and a large quantity of precursor chemicals.
"About 1,000 people have been extradited to the United States [where they are wanted on smuggling or money laundering charges]. We think we are winning this war. It won't be won in a short time-frame - just one or two years - but we will win it in the end."
Once the evidence had been gathered up from the crystallising lab, the Jungle Squad started hauling the various bits of illegal equipment into three big piles. Then, explosives experts started laying charges.
"Go time," one of the Jungle Squad said to me in English - to make sure I had understood.
The police use explosives to destroy illegal equipment and substances
"Vamos! Vamos!" others shouted. I do not speak Spanish - but I had seen the charges and I got the message.
I withdrew to a safe distance and lay down behind a grassy hillock in case the blasts reached me.
"Dos minutos!" someone warned. But they had got it slightly wrong. It was not two minutes before the first blast. It came almost immediately.
There was a big bang - muffled slightly by the surrounding jungle - then a whooshing sound as the chemicals caught light.
I looked in the direction of the blast and saw red flames licking through the deep green vegetation.
Then a thick column of black smoke rose skywards.
There were two more blasts. After the third and last, as the column of smoke got thicker and higher, the Jungle Squad whooped and cheered.
"Excelente!" one shouted. "Ole!" exclaimed another.
One lab down. But there are many more to go.