The network of cross-border tunnels remains a lifeline for hundreds of thousands of Palestinians

While Israel waged their bloodiest assault on Gaza in decades, their warplanes targeted tunnels on Gaza's border with Egypt in an effort to halt alleged arms shipments.

Now, Palestinians are busy restoring the bomb-damaged tunnels, and consumer goods are starting to flow into Gaza again.

Al Jazeera's Jeremy Young describes the process of filming inside them.

The famous tunnels in the southern part of the Gaza Strip are easy to find. 

Everybody knows where they are, but getting inside is another story.

Israel has maintained its blockade of Gaza, preventing goods from being imported, and Palestinians use the tunnels to transport every product imaginable from northern Egypt into the territory. 

The Israelis argue that the tunnels are used by Hamas to smuggle in weapons.

About 95 per cent of them were damaged or destroyed in Israel's recent three-week military assault on Gaza.

Our fixer had spent three days trying to get us access inside the tunnels. 

He said that he called 10 different tunnel operators and nobody would allow us to film there for fear that their tunnel might be targeted by an Israeli raid.

In the end, he succeeded and we arrived at 8:30 on Saturday morning at the first tunnel having agreed not to film any faces of the people that worked there. 

We sent Tony Zumbado, our cameraman and Mike Kirsch, our correspondent, inside the tunnel, which was at the end of a shaft about 20 metres deep. 

They used a pulley system, which is normally used to bring goods up and down, to send Mike and Tony down.

Al Jazeera interviewed Abu Wesam, a tunnel operator

This tunnel was not yet operational, as they were still making repairs after it was bombed during the war.

It extended an estimated 800 metres under the border and into Egypt.

While we were interviewing one of the tunnel operators, a senior supervisor arrived and began yelling and screaming. 

He was furious that we were filming there saying that they would get no benefit from our report. 

As our team moved to get back into our van, he said he would not allow it to leave and he would blow it up if we moved it.

He ran to the entrance of the tunnel and dragged barbed wire across to prevent us from leaving - tunnels are a serious business in Gaza and he had no interest in risking its future.

Trapped inside

The second tunnel we visited, they agreed to allow Tony to go down. 

This tunnel had been operational for just one day. Some of the items that they had brought up from it included generators, computers, rice, chocolate and powdered milk. 

Mike Kirsch speaks to Tony, our cameraman who was trapped inside the tunnel

The owner had spent about $90,000 on the tunnel, which was a joint operation with eight partners and it had opened only about one week before Israel's assault on Gaza began on December 27. 

Once Tony reached the bottom, however, the generator shut down. 

It took about 20 minutes for the tunnel operators to get the generator going again and Tony was successfully hoisted out.

At the first tunnel, the supervisor who was so angry about our presence, finally calmed down after about 15 minutes of rigorous negotiation from our fixer. 

He had demanded the material that we had filmed so we gave him one of our tapes, pulled the barbed wire back and drove our van out into the street. 

But then he walked over to us with tears in his eyes.

He apologised for his earlier explosion. 

He explained that the whole situation following the war was very difficult for everybody in Gaza and that was why he had lost control. 

He returned our tape to us and told us if we wanted to come back and film at the tunnel that we would be welcome. 

We told him that he had no need to apologise, thanked him and drove away.