A sinkhole found in eastern Iowa last week has continued to increase, just as Iowa officials prepare to try to figure out what caused it to start.

The sinkhole was discovered in Marion County, south of Knoxville. WHO-TV reports it's located in the 1700 block of 135th Place. That gravel road has been closed by Marion County Engineer Tyler Christian.

Google. Maps/Canva
Google. Maps/Canva

According to KCCI, the sinkhole was 30 feet wide and 20 feet deep when it was found last week. The road next to it was closed on Wednesday, April 12. It has continued to grow.

KCCI, YouTube
KCCI, YouTube

On Monday, KCCI reported the sinkhole is now 33 percent larger than it was several days ago. It's now approximately 40 feet across.

Although not yet confirmed, WHO-TV says there was once a 17-acre mine near the site of the sinkhole. According to the station, "It sits in an area where numerous coal mines were dug a century ago."

The Iowa Geological Society is scheduled to study the sinkhole sometime this week.

According to the Iowa Department of Natural Resources, coal was mined in 34 of Iowa's 99 counties, in central and southern parts of the state. Polk and Monroe counties, the counties with the largest areas mined, have more than 30,000 combined acres that were once coal mines.

Sinkholes aren't uncommon in Iowa, but ones the size of the sinkhole near Knoxville certainly are. Here are a few others. The first is what is more commonly seen:

Here is a very unique one:

And finally, one that made plenty of news in Iowa seven years ago. The ground gave way in an area of Des Moines where the South Des Moines Coal Co. once had a 203-acre mine, according to the Des Moines Register. The sinkhole developed in the front yard of a man's home overnight and was an incredible and terrifying 40 feet deep:

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