How can I cast a bytes32 to a BigNumber in ethers?

[outdoteth]

I have a hash string output from utils.keccak256 and want to convert it to a BigNumber.

[zemse]

const hexstr = "0x5fa2358263196dbbf23d1ca7a509451f7a2f64c15837bfbb81298b1e3e24e4fa"; // utils.keccak256('0x12')

const bn = ethers.BigNumber.from(hexstr);

The above gives you a BigNumber.