Several members of the expedition died there before the others realized the danger.

3 seconds sound clip from the 20 Million Miles to Earth (1957) movie soundboard.

You can hear this line at 00:30:14.846 in the Blu-ray version of the movie.

Quote context

[...]

- What I have to say you will find incredible, but true.

- Colonel Calder here has just returned from an expedition to Venus.

- To Venice. Perhaps you mean Venezia.

- To Venus. The planet Venus.

- The planet Venus?

- That is correct.

- I was informed this matter was connected with something vast, but the the planet Venus?

- Man's first interplanetary voyage. On the return trip, the spaceship was crippled by a meteor. Except for colonel Calder here, the entire crew perished.

- I am grieved.

- The problem that confronts us is this, signor. The atmosphere on Venus is such that a human being cannot breathe and survive for long, even after using what we considered foolproof respiratory equipment.

- Several members of the expedition died there before the others realized the danger.

- And Doctor Sharman, the chief scientist, also became fatally ill.

- He died here after the ship crashed.

- Fascinating. Horrible, but fascinating.

- Now, on that ship was a particular sealed metal container.

- In it is an unborn specimen of the animal life on the planet. We've got to find it.

[...]