Celebrities led by Sandra Bullock on Wednesday poured millions of dollars into relief efforts after monster storm Harvey ravaged Houston.

Bullock, who maintains homes in nearby Austin and New Orleans, donated $1 million through the American Red Cross, the organization said.

"I'm just grateful I can do it," Bullock, the star of Hollywood hits such as "Gravity" and "The Blind Side," said in a statement.

Socialite Khloe Kardashian said that her celebrity clan was donating $500,000 to the Red Cross and the Salvation Army.

She was responding to a challenge set by the comedian Kevin Hart, who on Tuesday said he was donating $25,000 and named celebrities whom he urged to follow suit.

In response, pop star Jennifer Lopez and her boyfriend, baseball legend Alex Rodriguez, in a joint Instagram post said that they were each donating $25,000.

"Seeing these pictures of children and all the footage, it's just devastating, and we just want to do our part to help," Lopez said.

Rapper Nicki Minaj, hip-producer DJ Khaled and actor and wrestler The Rock were among other celebrities to respond to Hart's challenge and donate $25,000.

The Rock urged Houston to stay strong and thanked Hart but, in perhaps an indirect criticism of the comedian's name-shaming, said he was "not going to call out my celebrity friends -- you guys already know what to do" and urged small donors to come forward with "a buck or two."

Chris Brown, the R&B singer infamous for his legal troubles, told Hart he was donating $100,000 but without explanation said his money "will go to the people" as he was skeptical of the Red Cross.

The country singer Chris Young also said he was donating $100,000 and urged fans to join him.

One of the most successful fund-raising efforts came from football player JJ Watt, a local transplant who plays for the Houston Texans.

After his online appeal quickly met his goal of raising $500,000 in donations, he repeatedly upped the challenge. By Wednesday he had raised $6 million and was seeking $10 million.

Beyonce, one of the top stars to emerge from Houston, and hip-hop mega-star Drake, who has a home in Houston, have both said they are working on generous relief plans but have not yet revealed the details.

Meanwhile, The Associated Press (AP) releases a list of stars who have publicly pledged to donate:

— Sandra Bullock, $1 million to the American Red Cross

— Leonardo DiCaprio, $1 million to the new United Way Harvey Recovery Fund

— The Kardashian family, $250,000 each to the American Red Cross and the Salvation Army

— Country singer Chris Young, $100,000 to the American Red Cross

— DJ Khaled, $50,000 to the American Red Cross

— The Chainsmokers, $30,000 to the American Red Cross

— Kevin Hart, $25,000 to the American Red Cross

— Dwayne "The Rock" Johnson, $25,000 to the American Red Cross

— Jennifer Lopez, $25,000 to the American Red Cross

— Alex Rodriguez, $25,000 to the American Red Cross

— Wendy Williams, $25,000 to the American Red Cross