BEIJING - Security was tight at Tiananmen Square today with little sign - other than a large police presence - of the 24th anniversary of the notorious crackdown on dissidents there calling for democracy.

The Chinese government has never fully accounted for casualties that day. Survivors say hundreds died when the military moved in to stop the peaceful protesters.

Our taxi driver was in Beijing during the uprising, but when asked by ABC News whether fewer people are talking about it these days, he replied, "Nobody even mentions it."

Tiananmen Square Remembered

When an ABC News crew arrived at the square, crowds were scarce and police officers were posted every few yards.

Within seconds I was stopped and asked to step aside. And within minutes two patrol cars arrived and five officers started questioning me.

Two of the officers filmed me, my ID and my bag. They were polite, but insistent. Because I did not have my passport, they said, I could not come in. The rules are that you do need a passport, but they don't usually check. Normally, anyone, including journalists, can enter the square with a camera and film. I have filmed at the square on other occasions without being asked for documents. On this day they checked my documents.

I was able to also film on my iPhone.

"We will give you an oral warning because you have forgotten your passport," an officer told me. "We don't care about the date. We care whether you have the correct ID card."

"But this is my ID card," I replied, showing them my press card.

The officer insists several times the check of my documents "has nothing to do with the date." But without my passport I am not allowed into the square.

I ask him, "Is today a difficult day to come shoot?" He answers, "We have no concept of that."

I am told to leave immediately.