This story was updated at 2:04 p.m.

More than a day after Yahoo News connected Donald Trump's name with the idea of setting up a Muslim database, and more than 19 hours after Trump used the words "absolutely" and "certainly" when asked by a NBC News reporter if he would implement such a database, the Republican frontrunner clarified his stance in a tweet that still left many questions.

Trump provided no details on who would be included on this watch list, how the information would be used or how this list would differ from those already used by the government.

The idea of setting up a database that tracks Muslims in the United States first came up in an interview Trump did with Yahoo News that was published Thursday morning. In that interview, Trump avoided taking a stance but raised grave concerns about Muslims in the United States. Then, on Thursday evening, Trump used the words "absolutely" and "certainly" when asked a series of questions by an NBC News reporter about implementing a database or system for tracking Muslims. Later that night, Trump refused to answer follow-up questions from other reporters. On Friday morning, a spokeswoman for the campaign, Katrina Pierson, was asked about the database on Fox Business on Friday morning, and said: "Trump is not taking anything off the table."

Although controversy over this theoretical Muslim database has dominated the news, Trump did not bring it up during a town hall at a college in Spartanburg, S.C., on Friday afternoon, despite promises from his staff that he would. During the event, Trump said that in the past few days he has shifted the focus of his comments from trade, job creation and global competitiveness to denouncing the Islamic State terrorist group, raising concerns about Syrian refugees and calling for a stronger military.

Even before the terrorist attacks in Paris, Trump said he would bar any Syrian refugees from coming into the country and, as president, would kick out those who are already here. He has also called for heavy surveillance of mosques and said he's open to the idea of closing some mosques. Other Republicans have picked up Trump's anti-Islam rhetoric in recent days.

In the Yahoo News interview that published on Thursday morning, Trump would not endorse or condemn a series of terrorism-fighting ideas like setting up a database, conducting warrantless searches or requiring Muslims to carry religion-identifying identification cards.

"We're going to have to do things that we never did before. Some people are going to be upset about it, but I think that now everybody is feeling that security is going to rule,” Trump said in the Yahoo interview. “And certain things will be done that we never thought would happen in this country in terms of information and learning about the enemy. And so we’re going to have to do certain things that were frankly unthinkable a year ago.”

That interview sparked rounds of questions, along with some criticism. On Thursday evening in Iowa, NBC reporter Vaughn Hillyard directly asked Trump about the possibility of a database of Muslims and Trump seemed to agree with the idea, using the words "certainly" and "absolutely."

Trump said the government should use "a lot of systems, beyond databases" to track Muslims, prevent illegal immigrants from entering the country and keep the nation safe. He added that he would employ "good management procedures" to get Muslims signed up for the database, although he did not say who would need to register under such a system and what penalties they might face for refusing. "You sign them up at different places," Trump said. "But it's all about management. Our country has no management."

Later in the evening, Trump demanded to know why reporters kept asking him about a Muslim database and would not take a position. When asked about the Yahoo interview, Trump said: "I never responded. I never responded to that question. ... I never responded. I don't know who wrote it, but I never responded."

Another reporter asked Trump to explain the difference between a Muslim database in the United States and the registry of Jews that once existed in Nazi Germany. "You tell me," Trump said. "You tell me. You tell me."

Trump's spokeswoman and campaign manager have not provided any more details on where the candidate stands on a Muslim database, instead referring reporters to the candidate's single tweet.

Jose A. DelReal contributed to this story.