Export high precision data to HDF5

Recently, I would like to use HDF5 instead of CSV because of times Import taking.
Especially, I have to manage large data with high precision (about 50 degits) and it takes very long time to export such data to CSV. Therefore, HDF5 seems nice to me.

However, when I do Import HDF5 file, I only get data with MachinePrecision.
On the other hand, CSV returns data with exact precision which I exported.

Here is a simple sample:

In[1]= data = N[Pi, 50];

In[2]= data // Precision
Out[2]= 50.

Then,

In[3]= Export["testing_precision_HDF5.h5", {data}];
In[4]= Export["testing_precision_csv.csv", data];

Finally I do Import and evaluate their Precision;

In[5]= Import["testing_precision_HDF5.h5", {"Datasets", 
    "/Dataset1"}][[1]] // Precision
Out[5]= MachinePrecision

On the other hand,

In[6]= Import["testing_precision_csv.csv"] // Precision
Out[6]= 49.4971

So, where does this difference come from? Is the reason why HDF5 takes short time to Import HDF5 cannot handle high precision data?

Please tell me how to manage high precision data with HDF5 & Mathematica.

Update: I don’t think it is a problem with ”’Import”’ because I checked the .h5 file with HDFview, but it was same result.